Chapter 12: ALKANES Flashcards
What is the general formula for alkanes?
CnH2n+2
What does branching do in alkanes?
Weakens the induces dipole dipole forces in the molecule, and lowers the melting point.
Are alkanes polar or non polar?
Non Polar.
Why does the boiling point increase as chain length increases?
London forces act between molecules in close surface contact. As chain length increases, the molecules have larger surface area, so more surface contact is possible between molecules. The London forces will be greater so more energy required to overcome forces.
what type of covalent bond is present in alkanes?
sigma bonds
When do sigma bonds form?
When electron orbitals from adjacent atoms directly overlap.
Are alkanes reactive or unreactive, and what can they react with.
They are relatively unreactive
Can react with radicals and halogens to form haloalkanes.
Are alkanes soluble?
Insoluble in water
What are the products in combustion of alkanes?
Carbon dioxide and water
What happens in incomplete combustion?
In a limited supply of oxygen, there is not enough oxygen for complete combustion. Carbon Monoxide (CO) is formed, and water. Soot may also be formed.
What is bond fission?
The breaking of a covalent bond.
What is heterolytic fission?
The bond breaks but electrons are distributed unequally to form 2 different ions.
Double headed arrow shows movement of a pair of electrons
What is homolytic fission?
The bond breaks with pair of electrons in the bond being shared equally to form 2 uncharged radicals.
What happens in initiation?
Radicals are produced normally using visible light or ultraviolet. Called photochemical reactions. The bond breaks producing 2 radicals.
What happens in propagation?
When a radical reacts with a non radical. New radicals are created which then go on to react with other non-radicals. This is why it’s called a chain reaction.
What happens in termination?
When 2 radicals react, they form a non-radical molecule. This ends the chain reaction.
Why are alkanes used as fuels?
They are readily available, easy to transport, and burn in a plentiful supply oxygen without releasing toxic products.
What is a pi bond?
Electron pair from overlapped p-orbitals forms a pi bond
What is the shape in alkenes around a carbon in a double bond?
3 bonding regions which repel equally so shape is trigonal planar and 120 degrees.
What are stereoisomers?
Stereoisomers have the same structural formula but a different arrangement of the atoms in space.
